This is not an answer, but I have same problem. Just want to share some observations from my side
I think there is something wrong with the mintAuthority
when minting
I'm able to run example from this document successfully https://developers.metaplex.com/candy-machine/guides/airdrop-mint-to-another-wallet#mint-without-guards, but if I replace this test wallet const walletSigner = generateSigner(umi);
by my wallet, I will encouter this error